Physiology of the Auditory System Flashcards

1
Q

Where is the basilar membrane displacement for high frequency noises?

A

at the base

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2
Q

where is the basilar membrane displacement for lower frequency sounds?

A

more apical

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3
Q

what is the structure of the membrane near the oval/round windows?

A

narrow and stiff

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4
Q

what is the structure of the membrane near the helicotrema?

A

it is wider and more flexible

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5
Q

how is the frequency of sound (pitch) coded?

A

by where along the basilar membrane there is greatest deflection

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6
Q

what type of cells are hair cells?

A

they are mechanoreceptors

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7
Q

what is on the apical end of hair cells?

A

stereocilia

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8
Q

what is the ion composition of endolymph?

A

it is high in K+ but low in Na+

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9
Q

where is endolymph found?

A

it fills the cochlear duct and the membranous labyrinth ; found in the scala media

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10
Q

what is endolymph produced by?

A

stria vascularis

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11
Q

what is the composition of perilymph?

A

it is potassium poor- low K+ but high Na+

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12
Q

where is perilymph found?

A

it is found in the scala vestibuli and scala tympani

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13
Q

what does the perilymph bathe?

A

the basal end of the cochlear hair cells

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14
Q

what does the endolymph bath?

A

the apical end of the hair cells

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15
Q

what happens when there is a pressure differential that will bend/ pivot the stereocilia in the direction of the longest stereocilia?

A

K+ ions will enter the cells and depolarize the cell

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16
Q

what are the specific Ca2+ ion channels that open due to a change in voltage?

A

TRPA1

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17
Q

deflection of stereocilia that causes depolarization will cause what?

A

release of the NT glutamate and a generation of action potentials in the 8th CN nerve fibers

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18
Q

what happens when there is deflection of stereocilia towards the shortest stereocilia?

A

hyperpolarization

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19
Q

what is the main role of the stria vascularis?

A

it maintains the electrochemical properties of the endolymph aka it keeps the scala media very highly concentrated with potassium

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20
Q

what forms the blood-labyrinth barrier?

A

the high endocochlear potential drives positively charged ions into the hair cell down its concentration gradient

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21
Q

what is a common source of ototoxic drug secretion into the cochlea?

A

the stria vascularis

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22
Q

what is the primary function of the inner hair cells?

A

these are the primary source of auditory information

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23
Q

what is the primary function of outer hair cells?

A

there are the primary cells that amplify sound waves; they are also contractile

24
Q

what are the olivocochlear efferents?

A

when the ear itself produces a sound- movement of the basilar membrane toward the oval window and through the middle ear

25
Q

what neurons innervate outer hair cells?

A

medial olivary complex neurons

26
Q

what neurons innervate inner hair cells?

A

lateral olivary complex neurons

27
Q

how can olivocochlear efferents be measured?

A

in the external auditory meatus as otoacoustic emissions (OAE)

28
Q

what is the clinical significant of OAE?

A

newborn hearing screening, ototoxicity, tinnitus

29
Q

what makes up the cochlear nuclear complex?

A

the ventral cochlear nuclei and the dorsal cochlear nuclei

30
Q

what is the role of the dorsal cochlear nuclei?

A

it integrates the acoustic information with somatosensory information

31
Q

what is the role of the ventral cochlear nuclei?

A

it begins processing the temporal and spectral features of the sound (nature of the sound- high/low)

32
Q

where is the first site in the brainstem where information from both ears converges?

A

the superior olivary complex

33
Q

what is the role of the superior olivary complex?

A

binaural processing

34
Q

what is binaural processing essential for?

A

to accurately localize sound

35
Q

what makes up the superior olivary complex?

A

the medial superior olivary nucleus and the lateral superior olivary nucleus

36
Q

what is the role of the medial superior olivary nucleus?

A

localizes sound due to differences in TIME of arrival to ears

37
Q

what is the role of the lateral superior olivary nucleus?

A

localizes sound due to differences in INTENSITY of sounds between ears

38
Q

what is the role of the inferior colliculus?

A

it suppresses information related to echoes and arrives at a final estimation of localization of sound along the horizon

39
Q

what is the relay station in the auditory pathway?

A

the medial geniculate nucleus of the thalamus

40
Q

what is essential in the conscious perception of sound?

A

the primary auditory cortex

41
Q

how is the set up of the primary auditory cortex?

A

more rostral areas are activated by low frequencies and more caudal areas respond to higher frequencies

42
Q

the auditory (secondary) association cortex is composed of multiple areas including what?

A

Broca’s and Wernicke’s

43
Q

what does the auditory association cortex respond to?

A

more complex sounds such as music, identifying (naming) a sound, and speech

44
Q

where do olivocochlear efferents originate?

A

in the superior olivary complex

45
Q

what is the primary role of the olivocochlear efferents?

A

they decrease basilar basilar membrane motion- reduces responses to noise- may protect hair cells from damage to intense sounds

46
Q

the middle ear efferents include motor innervation to what?

A

tensor tympani to the malleus and tympanic membrane and the stapedius to the stapes

47
Q

when do middle ear efferents act and what may they prevent?

A

they act at low frequencies and they may prevent damage

48
Q

what is sensorineural hearing loss caused from?

A

damage to the hair cells or nerve fibers or both

49
Q

injury to outer hair cells causes what?

A

decrease in sensitivity

50
Q

injury to inner hair cells causes what?

A

it cuts off auditory input to the CNS

51
Q

what is the anterior semicircular canal activated by?

A

rotation in the vertical plane forwards (falling forward)

52
Q

what is the horizontal semicircular canal activated by?

A

rotation in the horizontal plane (twirling like ice skating)

53
Q

what is the posterior semicircular canal activated by?

A

rotation in the vertical plane backwards (falling backwards)

54
Q

what is the utricle activated by?

A

linear acceleration forward and backward (running)

55
Q

what is the saccule activated by?

A

linear acceleration up and down (dunking a hoop)